Automatic stoker



Feb. 8, 1944. A. wlN-l-ER 2,341,252

AUTOMATIC STOKER Filed March 31, 1941 3 Sheets-Sheet l.

Feb. 8, 1944. l. A. WINTER AUuToMATIc sToKER Filed March 51, 1941 5Sheets-Sheet 2 ATTORNEYS.

Feb. 8, 1944. 1 A wlmTER 2,341,252

AUTOMATIC STOKER Filed Marchl, 1941 3 Sheets-Sheet 5 II'IIIE l l l l l77 S s. 1N VENTOR:

MAQ

BY y v y ATTORNEYS.

Patented Feb. 8, 1944 UNITED STATES PATENT OFFICE 2,341,252 y vaurolmrricl sToKER Ireal A. Winter, Birmingham, Ala. ApplicationMarch31, 1941, Serial No. 386,153

9 Claims.

This invention relates to automatic stokers for the burning of solidfuel, and particularly to fully automatic stokers and ash removalsystems for use in home and apartment house heating plants,

and in industrial installations.

Objects of the invention are to provide automatic stokers of noveldesign, and of novel combustion characteristics, in which various typesofl anthracite and bituminous coals may be burned with equal ease andfacility. An object is to provide an automatic'stoker in which the fueland air passages are sol related, and the ash is continuously removed insuch manner, that the fuel burns with a torchlike flame. An object is toprovide an automatic stoker including a rotary hearth, mechanism forfeeding crushed coal upwardly through the hearth, passages for supplyingcombustion air at regions that result in'a fuel bed of substantiallyconstant depth and surrounded by an ash bed that protects the hearthfrom damage, and devices for agitating the ashes and preventing theformation of a clinker ring. A further object is to provide an automaticstoker of the stated rotary hearth type in which the hearth is retainedupon its support by the weight of the hearth and the coal and ash uponthe hearth, the hearth being rotated by a rotary screw conveyor thatremoves the ashes to a remote point.

These and other objects and advantages of the invention will be apparentfrom the following specification when taken with the accompanyingdrawings in which:

Fig. l is a plan view of a Stoker and automatic mechanical ash removerembodying the invention;

Fig. 2 is a side elevation of the same;

l Fig. 3 is a fragmentary end elevation, with parts in section, asviewed from the plane indicated by line 3-3 of Fig. 2;

Fig. 4 is a fragmentary transverse section, on

an enlarged scale, taken on the plane of lineA 4 4 of Fig. 3;

Fig. 5 is a fragmentary section taken on the plane of line 5-5 of Fig.4;

Fig. 6' is a fragmentary section, on an enlarged scale, taken on theplane of line 6-6 of Fig. l1;

Fig. 7 is a fragmentary horizontal section taken on the plane of line'I--T of Fig. 6, with parts broken away to show the rotating elementsinplan;

Fig. 8 is a fragmentary vertical section through the burner, and showsthe combustion phases, air flow and other elements of the burningprocess;

Figs. 9 and 10 are fragmentary transverse sec tions on the planes oflines 9 9 and lil-I0, respectively, of Fig. 6;

Fig. 11 is an enlarged and fragmentary plan view of the rotating hearthandtuyre;

Fig. 12 is a-sectional view taken on the plane of line I2-I2 of Fig. 11;

Fig. 13 is a fragmentary plan View of another embodiment of theinvention that includes an automatic pneumatic ash remover; i

Fig. 14 is a fragmentary section, on an enlarged scale, taken on theplane of line I4-I4 of Fig. 13; y p

, Fig. 15 is a vertical section taken on the plane of line I5 -I5 ofFig. 14;

Fig. 16 isa fragmentary enlarged section taken on the plane of lineIG--IB of Fig. 15; and

Fig. 17 is a'fragmentary section taken on the plane of line I'I-II vofFig. 16. In the drawings, the reference numeral I identitles a motorthat drives the blower 2 and the associated fuel feed mechanism by whichthe combustion components, i. e., air from the blower 2 and crushed fuelfrom the hopper 3, are supplied to thel burner 4through the dualpassages of the tubular member 5. The burner is located in the usualposition within the furnace 6, and ashes are removed from the interiorof thefurl nace through an ash tube 1 and deposited in an ash hopper 8.The volume of air delivered to the burner through the air passage 9 atthe bottom of the tubular member 5, see Figs. 3,` 6 and 9, is regulatedby the thumbscrew II) that controls the air inlet opening II between theblower manifold and the intake orifice plate I2.

The blowershaft is directly driven by the mol tor shaftbut thefffuel andash conveyors are driven at low speed, and intermittently, through atransmission including sheaves I3, I4 on the motor shaft and acountershaft I5, respectively, and a V-belt I6. The shaft I5 carries aneccentrically mounted roller bearing I'I that imparts rotation to thefuel feed drive shaft I8 through the ratchet wheel I9, spring-returnedpawl 20 and rocker arm 2|. Y The eccentricity of the ball bearing II isadjustable by known mechanism, not shown, to provide a regulation of therate of fuel supply. u v

A shear pin 22 couples the hub ofthe ratchet wheel I9 to the stub shaftI8 to prevent damage upon a fouling of the fuel feed screw 23 that has asquared end seated in a correspondingly shaped socket in the enlargedinner end of the shaft I8. A lubricated roller bearing. is mounted onthe sheave guard 25V to support the stub shaft I8, the

alinement ofthe aShscrew shaft. 3| whilefthe felt packingsr 34 protectthe bearings' from the in# trusion of coal dust from the hopper. Theenlarged end of the drive shaft |8 extends into the;

fuel hopper through the housing plate 21, and a felt packing 36 sealsthe shaft to prevent the escape of fuel at this point.

The upper passage of the tubular member comprises the fuel feed tube 38that is turned upwardly, at its inner end, to open into and toY supportthe stationaryv conical retort 39, that flares outwardly to terminate ina slightly concaved annular flange 4|). The burner ring or rotatinghearth 4| is locatedimmediately -above the flange 4U and a large numberof tuyre oriilces 42 are provided betweenthese vmembers to admitcombustion air to the Aretort and hearth from the annular air chamber 43at the upper end of the air supply passage 9. The tuyre orifices arepreferably formed in the base of the rotating hearth by deep notchesbetween the lugs 44 that have lower faces conforming to the curvature ofthe flange 4| and rspaced from the flange by a small clearance of, forexample, about '12 inch. The cross-sectional area of each tuyre issubstantially constant,` and the air velocity through the tuyre istherefore practically constant, but the circumferential lengthV and theaxial height of the tuyre vary progressively along the radial length ofthe tuyre to provide a longand shallow inlet opening at the outer edgeof the hearth 4| Aand a short and deep outle opening at the inner edgeof the hearth.

As shown in Figs.`6, 7, 11 v'and l2, the side walls ofv each tuyre oriceare plane surfaces, and the top and upper walls are conical surfaces ofdifferent slope comprising, respectively, the flange 40 and the uppersurfaces of the hearth 4| between the lugs 44. The inner ends of thetuyre orifices are approximately Square With an aggregatecircumferential length of about 180, and a relatively large number oforifices are used to distribute the airv efnciently around the burnerand to direct the jets into the` fuel bed. Any ash or small Aclinkersthat may collect in the tuyre orifices 42 and on the retort flange 40,during periods of quiescence when the burn-` ing is vof Aa slowsmoldering character, are loosened and scraped back into the retort by aplowing action of the lugs 44 or are blown back by the air blast. l

The hearth 4| is rigidly secured by screws 45 to the ash scraper ring46- that is 'intermittently rotated by the attached tooth ring -41 anddrive pins -48 on`a collar 49 on the end of the ash conveyor screwv 5|,Figs. 6, 7 and 9. 'The collar 49 is lubricated by a spring loadedgraphite stick 5U carried by the casing. The pitch ofthe pins 48 issomewhat greater than that of the teeth Aof thering 41 andthe centerlineof the ash screw 5| and collar 49 is offset from the axis of thetoothedring 41, thus limiting the engagement of the drive pins 48 with theteeth 41 to a horizontal approach to and a downward movement alongthevertical flanks of the teeth. This :operating characteristic isimportant since the hearth 4| and the ash scraper ring 46 are retainedin place on the burner solely by their weight. Supporting wheels 52 aresecured to the ring 46 between certain of the radially project 5 ingfins 53, the wheels being mounted on inclined shafts 54 for supportingthe hearth and ash scraper ring upon the housing member 55. Thedouble-coned Wheels 52 roll along the inner edge of the annular flange55' that projects radially from the housingmember.v 55 at--a pointslightly lbelowits: upper `edge.y Theupper part of the member 55 thusforms a cylindrical guide for centering the rotatable assembly tomaintain a small clearance 56 between the ash scraper ILS-ringl 46 vandthe housing member 55. This clear- Y ance is essential as the resultingflow of air from Vthe annular` chamber 43 sweeps across the supl portingflange 55 to remove ashes from the wheel track and to provide preheatedsecondary air for rapid and efficient combustion of gases above the fuelbed. Additional preheated-secondary air is supplied through the annularorifice 59 be# tween the upper edge of the ash scraper ring 46 and thehearth 4|.

A rake 63 is hinged upon the open topped ash hopper 64 that is securedto the housing `55 of the burner and supports the inner end'of the ashremoval tube 1, Figs. 1,' 2 and 6. 'I'herake 63 is a tapered metal platewith its smaller end or point resting upon the edge of the rotatinghearth 4| to agitate the ash bed and prevent the formation of the largeannular clinker ring that is characteristic ofrsome prior rotatinghearth burners. The hingedmountingof the rake pe r mits Yeasy removal ofthe hearth and ash scraper ring, and also permits the rake to ride overany unburned embers that may be present in the ash, thus serving toexpose thel embers to the surrounding air .to facilitate completecombustion. The tapered rconstruction of the rake protects itfromdestruction as'the large radiating surface outside of the yfuel beddissipatesheat more rapidly v'than it is absorbed by the smallinnerendthat -is exposed tothe ash and fuel bed. Theash conveyorscrew 5|is connected to the ash screwshaft 3| bv a coupling 65 and shear pin EB.An agitating arm 61. is secured to the ash screw within the discharge T68 from which the outlet branch 69 slopes upwardly to deliver the ashesto the ash can 8. The-agitating arm 61 prevents the ash from packingtightly in the end of the discharge T, and stirs and aerates the ash tomaintain the condition of vsemi-fluidity that is essential to a freeflow of the ash.` The blade of the ash screw 5| does not extend to theagitating arm 61 but terminates at about the center line of the outletbranch 69, thus leaving a small space in which the ash is relatively atrest. The agitating arm and the exposed end of the screw move the ash upthe outlet branch by a pumping action at each rotation of the ash screwand, since the displacement of the ash screw is about three times thevolume of ash being removed, the zone of non-agitation forms a storagepocket that prevents a-constant grinding of the ash between the rotatingparts and the. wall of the discharge T. The crosssectional area of thedischarge branch '69 increases towards the discharge end to prevent theash from packing, the increase being equivalent to that of a conicaltube of from 2 to'5 total included angle. The cross-section of theoutlet branch preferably varies progressively from a square inner end,Fig. 6, to the cylindrical'outer endk upon which the thin conical shield1|lis semblingplastic flow, andthe upward inclination of the dischargebranch. 69 provides a. body of ashes that forms a seal to. prevent theescape of pressure air, and? entrained fine ash, from` the interior ofthe furnace. f

The phases and. elements of combustion. for the burner are illustrated.Fig. 8'. The body of fuel Ay is. forced' upward. into thef conicalretort. 39` byA the feed screw 2.3, and' is ignited in the regionf B byair. blastsfa that are directed inwardly through the tuyrev orifices 42;The fuel bed: is agitated bythe intermittent rotation off the hearth di,through the toothed wheel 4"| and pins 48; and. theair readilypenetrates tothe interstices of the burn'ingfuel and effects rapid and'eicient combustion.. A lportionV of the air and gas'.l which has' beenpreheated in the-annular combustion region B isv forced infwardiy tosupplement' radiant heat from'` region B in preheating the fuel in theinteriorI vzone C, thereby driving off the gas and volatile mat,-

ter to form a cone D above the fuel bed'. The

remainder ofy the primary air: fromthe tuyre serves to complete the'combustion of the outwardly mushrooming degasifiedi fuel from the regionC, while preheated secondary air issues from the annular orifice 59 and.the clearance 5S; as indicatedv by arrows b, c, respectively, to effectthe complete combustion ofthe gases of cone Dr in the torchlike flameE.` These secondary air'streams flow alongthe rotating hearth and ashscraper ring to protect-them against overheating and warping.

The bed E of ashes and embers whicheverlies the outer flange of therotating hearth 4| acts as an insulation for the hearth and also servesto maintain a fuel bed` of sufficient depth to' force the air blasts ainto the incoming body of fuel: A to preheat it, and to prevent theyupwardly moving air streams from blowing` the fuel from the. burner atthe. combustion region B. The depth of the burning region Bis thusgovcrned by thev slope ofA the outer ange' of the hearth 4|, and thisslope may be selected in accordance with the weight and burningcharacteristics of the fuel. TheV illustrated slopev of about 35 degreesis appropriate for various grades of lignite, bituminous and anthracitecoal bu-t a 'greater slopev may affordA more efficient operation whenburningcoke or sawdust.

The described process ofr burning the fuel results in a high burnereiiiciency, both with respect to the quantity of fuel-which may' beburned; in a. given time and with respect to; the heat value receivedper. unit of fuel. Further, since; com.- bustion withinthe burner isconfined tothefsmall annular region B and producing a name which, bothin appearance and the rapidity with which it builds up from quiescence,resembles that produced by an oil burner, overheating of the parts isprevented as is attested by the fact that after a short period ofquiescence during which burning recedes into the retort, the ashes canbe scraped away and the burner lifted out using only a gloved hand. Theprotection of the burner parts from destructively high temperaturesresults from the described paths of ow of the combustion air through andaround the burner. The combustion zone B is spaced from the metal parts.by the incoming fuel A. or by the ash bed F; and the secondary airstreams ow along: and

.cool theouter'portion ofthe burner, being thereby-l preheated to effecta quick and eiiicient com'- bustion ofthe gases that rise above the fuelbed.

The supply of fresh fuel forces ashes outwardly from the rim of the ashbed F, and this .flow is.v facilitated by the slight shaking actionresulting from the-step-by-step movement of the rotary hearth. 42| andby the' scraping action of rake 63` that prevents the formation of aelinker ring; The ash falls upon the radial ange 55" .of the housing 55,and is swept along the ange and into the ash hopper 64 by the ns 53 ofthe ash scraper ring 4B. The removal of ash is essential to stableburner operation and the illustrated construction has a number ofstruc'- tural features or operating characteristics. that are of majorimportance. It is essential that the clearance between the radial flange55 and the lower edges of the ash scraping fins 53 be small. Ashes andclinkers are forced along the flange by the ns 53, and the clearancemust be limited to prevent clinkers from lodging under the ns and thuslifting the hearth 4| that is retained in` position by gravity,Another-feature that prevents an inadvertent lifting of the hearth isthe cutting back of the ash screw 5| so that no part, or only a smallpart, of the screw extends beheathV the ns 53. InsuiicientV clearance atthis point might allow clinkers to jamb between the screwV 5i and thefins 53, thereby lifting the hearth 3| to disengage the toothed wheel 41from the drive pins 118 andv thus preventing further rotation,

A relatively large quantity of ash will accumulate within the burnerAduring quiescent operation and, when thev burner isagain operatedA atfull capacity', the rate ,of ash discharge from the burner mayv exceedthe capacity of the ash screw 5| for ashort interval; The excessquantity of ashes is temporarily stored upon the flange 5'5' of thehousing 55, between. the iins 53, and is eventually removed through theash hopper 64 when the ash screw catches up? with the rate of ashdischarge.

In an alternative embodiment of the invention, as shown in Figs. 13 to17, inclusive, the ashes are removed by a pneumatic system. In general,the burner and` associated mechanisms may be substantially as previouslydescribed and like parts are therefore designated by correspendingVreference numerals but will not be described in detail.

They drive pins 48 for the rotary hearth are carried byr a shaft 5| thatis. alined with and coupled: to the shaft 3|-, The shaft 5| extendsthrough the ash hopper l2 and carries Crusher Wheels i3 for breaking upclinkers before they enter'tl'ie` outlet sectionV I4 of the ash hopper.The ashes and. finely ground clinkers that col.- lect in the section 14are sucked away and blown into the ash can 15- by the ejector 'I5 whichreceives an air blast. through the connecting pipe 'Hf that extends intothe pressure air passage 9. The air and ash stream is delivered to theash can 'l5 through the tube I8 which has the diffusing section 'i9 fordecreasing the velocity of the stream as it approaches the ash can. 'Iheair and ash stream enters the ash can tangentially and the impartedswirl will effect a separation of the solids from the air by centrifugalforce. The air vent is placed at the center of the can where thesuspended ash is at a minimum; but as a further precaution against theescape ofV nelydivided ash and gas, the vent pipe 8l) is carried to theintake orifice on the blower 2, thus providing a closed circulationsystem which aidsV in removing ashes to the ash can 'l5 by reducing vtheback pressure on the ejector 1G.

The ash can 15, which for convenience of i1- lustration has been shownadjacent to the stoker,

canv be located anywhere that may be desired, such as in the alley, inwhich case the vent'80 a' vention.

I claim:

1. An underfeed stoker comprising a stationary upwardly flaring conicalretort member, a rotatable annular hearth member supported above andconcentric with said retort, means for forcing fuel upwardly throughsaid retort and hearth member, a pressure air chamber surrounding saidretort, said annular hearth member having tuyre passages in theunderside thereof for discharging air from said pressure air chamberradially into the fuel bed and having a conical upper surface slopingoutwardly and upwardly from the upper end of said stationary retort forsupportingan annular fuel and ash bed of suflcient depth to coni-lne theiiow of airentering through said tuyres to the central portion of thefuel bed within the hearth and retort, and means for rotating the hearthmember.

` 2. An underfeed stoker as claimed in claim 1, in combination -urith ahorizontally hinged rake mounted laterally of the hearth and having thetip thereof resting upon the upper edge of the rotatable hearth, therebyto'prevent the formation of a clinker ring about the combustion zone.

3. An underfeed stoker comprising an upwardly aring conical retortmember terminating at its upper end in an outwardly flaring annularflange, a rotatable hearth member disposed above said annular flange,means for forcing fuel upwardly through said members, a pressure airchamber surrounding said retort, and tuyre orices comprising recesses inthe under surface of said hearth member facing the annular iiange ofsaid retort, wherein each tuyre orifice is of substantially co-nstantcross-sectional area through the length thereof, and is of less heightat its air entrance end than at its air discharge end.

4. An underfeed stoker comprising an upwardly flaring conical retortmember terminating at its upper'end in an outwardly fiaring `annular`marcate flange, a rotatable hearth member disposed above said annularflange, means for forcing fuel upwar-'Lilyv through said members, apressure air chamber surrounding said retort and multiplicity 'of Vtuyreorifices comprising recesses in the un- Ader surface vof said hearthmember facing the annular flange of said retort, said multiplicity oftuyre orfices having an aggregate circumferential length ofapproximately at the interior wall of the member in which saidorince-defining recesses are formed, each adjacent pair of recessesbeing spaced apart at said wall byan extension of the member ofsubstantially the same circumferential length as said recesses.

5. In an underfeed stoker, a stationary conical retort, a rotatablehearth above said retort and having an outwardly and upwardly flaringashsupporting flange, and a horizontally hinged rake supported laterallyof said hearth and having an active end thereof resting with a linecontact upon the edge of said rotatable hearth and adapted to extendinto a bed of ash adjacent the edge thereof, said rake being tapered topro'- vide a large heat-radiating surface spaced from the hearth to coolthe small active end of the rake that 'contacts the hearth and the ashbed upon the same.

6. In an underfeed Stoker, a stationary conical retort, a housing membersurrounding said retort having a radial flange adjacent the upper endthereof, a rotatable assembly comprising an annular hearth member ofless circumference than said flange disposed above and concentric withsaid retort and an ash scraper ring secured to said hearth member andhaving radial fins extending over said flange on said housing member,wheels mounted on said rotatable assembly and bearing on said flange tosupport said assembly thereon, an ash hopper adjacent said housingmember positioned to receive ash falling on said flange over the edge ofsaid hearth and swept from said flange vby said i-lns, means forremoving ash from said hopper, means for forcing fuel upwardly throughsaid retort and hearth,

meansfor forcing air into said housing and re- Etort and means forrotating said assembly comprising said hearth and ash scraper ring.

'7. In an underfeed Stoker, the invention as claimed in claim 6, whereinsaid wheels support said assembly above said flange to provide anopening through which air flows to blow ashes from said fiange, therebycleaning the track upon which said wheels rotate.

8. In an underfeed stoker, the invention as claimed in claim 6, whereinan annular air orifice is provided between said hearth and said ashscraper ring to direct 'a cooling stream of air along the lower surfaceof said hearth.

`9.. In an underfeed Stoker, the invention as claimed in claim 6,wherein said housing member extends above said flange to provide acylindrical surface engaged by` said wheels to center said rotatableassembly above said retort.

IREAL A. WINTER.

